Carb questions re: 78 GS750E

[Silvia96]

New to this site but not to these bikes, and I had a couple quick questions. I've been searching through all the pages of the forums for a couple of weeks now, and am currently working on getting the bike to run right with the pod filters and an open 4-1 exhaust. I've got a friend whose passion is motorcycle carbs, so that helps. We've been playing with the jetting on it for a couple of nights now, but to no avail.

I see pretty much everybody on this site is recommending that people in my position should just go ahead and order the stage 3 kit from DynoJet, but on every website, this kit is only available for the 1980 and up 750's, which I am assuming use different carbs. So while I could order a larger main and maybe up the pilot a stage or two, I'd really like to go ahead and order this kit, as those adjustable needles would come in handy.

So where can I get a kit for the 78?

You guys seem to be a great group of like-minded enthusiasts. Glad I found this website.

[tkent02]

There is no kit sold for the '78 750. It's pretty easy to get it right using Mikuni jets. Keep the same pilot jet, maybe raise the needle one notch, up the main jets to about 122.5 or 125 or thereabouts. Plug chops will tell the story.
Fine tuning as always will take time and effort.

[Silvia96]

Thanks for the quick reply. At this point the bike won't even start, it just cranks and cranks. Getting plenty of spark, so I'm sure it's fuel/air. Since it won't even idle, I'm sure the main jet isn't the problem. I'll raise the needles a notch, throw in some 125's, and hope for the best.

[tkent02]

Take the carbs apart and clean them first, it's sure to need it. The smaller pilot circuits and choke supply passages are always the first to clog up from sitting. Read the tutorial on this site for cleaning VM carbs, it shows most of what you need to do.

[Silvia96]

Cleaned them thoroughly the first time we took them apart to check all the settings and sync them.

[BassCliff]

Greetings and Salutations!!

Hi Ms. Sylvia96,

I'd like to share some GS lovin'.

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If there's anything you'd like to know about the Suzuki GS model bikes, and most others actually, you've come to the right place. There's a lot of knowledge and experience here in the community. Come on in and let me say "HOoooowwwDY!"....

Here is your very own magical, mystical, mythical, mind-expanding "mega-welcome". Please take notice of the "Top 10 Common Issues", "Top 15 Tips For GS Happiness" the Carb Rebuild Series, and the Stator Papers. Now let me roll out the welcome mat for you...

Please click here for your mega-welcome, chock full of tips, suggestions, links to vendors, and other information. Then feel free to visit my little BikeCliff website where I've been collecting the wisdom of this generous community. Don't forget, we like pictures! Not you, your bike!

Thanks for joining us. Keep us informed.

Thank you for your indulgence,

BassCliff

[verde]

Hey Silvia,

Going through the same thing with a similar set-up(only wish I had a 4->1 so I could make my own pipe more easily) Just bumped up to 20's for pilots and it's feeling a lot closer.

I have no affiliation with these guys, just a happy customer. If you don't have jets readily available, their shipping is always quick. Between 4 bikes I've probably spent 1/3 months rent on jets from these guys just because I like to have a wide range on hand.

http://www.jetsrus.com/a_jets_by_carburetor_type/jets_mikuni_N100-604_main_Large_round.htm

http://www.jetsrus.com/a_jets_by_carburetor_type/jets_mikuni_VM28-486_pilot.htm

[Steve]

If your carbs are clean and you are getting spark, but it still won't start, adjust the valves.

As our bikes age, the valves get tighter. Tight valves are notorious for hard starts when cold.

.

[Silvia96]

Good advice. We're gonna go ahead and do the valves next, once I have the carbs off again to put in the larger mains and raise the needle a notch. I went ahead and ordered some 17.5 pilots, looking like that should run right for my setup. I'll let you guys know if I can get her going!

[Dave8338]

Grab a spray bottle and throw some 2-cycle fuel mix 50:1 at it and get the pig to start and "run" as you tinker.

Starting a "cold" as in, untested set up, is hard enough to get lit.

Once you can get it to make its own heat, you have half the battle won.

[verde]

I went ahead and ordered some 17.5 pilots, looking like that should run right for my setup.

That's funny. After a needle adjustment to get the mid range right, I've just come to the conclusion that I probably overshot on the plots and will bump down to the 17.5's

[Silvia96]

Verde,

Your comments on your bobber thread influenced that choice of the 17.5's!

[chuck hahn]

Set the pilot screws ( on the bottom ) at 1 1/4 out and the air screw ( on the side ) at 2 turns out. That should get you in the ballpark for fuel / air mixture. My buddies 78 750 E seemed to do best with 102.5 mains with the Vance and Hines 4 into 1 exhaust. Clip on the center notch.